MINOR: dns: new DNS options to allow/prevent IP address duplication

By default, HAProxy's DNS resolution at runtime ensure that there is no
IP address duplication in a backend (for servers being resolved by the
same hostname).
There are a few cases where people want, on purpose, to disable this
feature.

This patch introduces a couple of new server side options for this purpose:
"resolve-opts allow-dup-ip" or "resolve-opts prevent-dup-ip".
4 files changed